1. FIELD OF THE INVENTION
This invention relates to a new and novel type of microscope, and more particularly to a microscope which renders phase gradients in phase objects visible by virtue of operating on portions of the amplitude of light passing through the Fourier plane, thus converting phase gradient information to intensity variations.
2. DESCRIPTION OF THE PRIOR ART
Objects examined under the microscope by either transmitted light or reflected light create an image by virtue of absorbing some of the light transmitted through or impinging upon the object. Such objects are known as amplitude objects. By virtue of the special characteristics of this invention, such amplitude objects are revealed more clearly, with greater detail and additional information which would not be visible. Other types of objects which are transparent or nearly transparent cannot be seen under the ordinary microscope with ordinary illumination, and are known as phase objects. Such objects retard or advance phase of the light wave passing through the object. Since the eye is sensitive to intensity and not to phase, such objects are invisible. Other microscope systems have been designed to convert phase changes into amplitudes or intensities, rendering the phase information in the object visible.
Existing microscopes which convert phase information into intensity differences, such as the phase microscope and the interference microscope, do so by interference effects which are produced in the image plane between two or more waves of light which have been split, separated by one means or another in the optical path of the microscope. The resultant interference between the waves of light passing through unchanged in phase and those which have been diffracted by the object produce intensity variations. In the phase contrast microscope, phase objects are rendered visible by the interference produced between the beams of light which pass through the object without deviation and the rays of light which have been deviated by the object. The phase difference introduced by the phase plate in the phase microscope is a design feature that renders visible small phase features of the object. Also, by virtue of the manner in which the phase plate is illuminated and constructed, a halo is produced around diffracting and refracting features of the object which obscures the boundaries of such features, rendering the phase microscope unsuitable for precise measurement of dimensions. The interference microscope, full duplication or differential type, produces interference at the image plane between two beams of light solely due to their phase difference.